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Slow motion reverse flow 300 gal. - Page 3

post #41 of 72
Thread Starter 

Getting the firebox welded up!





The doors open up like you were in a storm cellar.

post #42 of 72

It's good to see you really "get into" your work. laugh1.gif


Looks great DB!

post #43 of 72
Thread Starter 

I've been dragging my feet but I'm ready to get on with this build.


I sanded the old paint off the door and painted it. Progress!


I also hole sawed out some 1/2" flat bar for the firebox door latch.



I have a couple of topics of discussion that I'm interested in some feedback.


First the issue of the traditional RF smoker. I've been thinking about how to cool down the hot spot I have in the middle and still have the efficiencies of a center fired smoker. Last night I had a dream. I do some of my best design work asleep! I'm going to try a heat shield just above the firebox dampers and below the RF plate. Might get a percentage of heat control. I can't modify Dragon's Breath but this will be a perfect control test with the new smoker.  I thought about using SS sheet metal for longevity. I have read on some of the builds here that sometimes some kind of heat shield is use on the traditionals.


The second topic is bimetal hinges. I believe that using stainless pipe with mild steel round bar or visa versa will result in a more lasting hinge that won't freeze up. My thoughts are the mild steel would have nothing to rust to and the stainless steel wouldn't gall.

Any thoughts would be welcome.



post #44 of 72
Thread Starter 

I came up with another issue that is specific to center fired RFs. I tapered the drain angle on the RF plate on Dragon's Breath as I had seen others do but I believe that is what makes my smoker cooler on one end than the other. This time I am positioning the RF plate level with the smoker. As I sometimes use a level to set up the smoker I just don't want to list it to the side to take into consideration of the RF plate being tilted. Now I should be able to control the side heat better.



What do think?



post #45 of 72

Dave, evening....... center feed smokers ....   they are beyond my simple mind as far as being able to guess what they will operate like....   Sorry I'm no help here.....



post #46 of 72

What if you tapered it to a low spot center front, similar to the way mine is tapered to a low spot to the extreme left and centered front to back. My thinking being that as the heat raises and travels the path of least resistance, it would in effect solve both issues by distributing heat more evenly. Just a thought.

post #47 of 72
I am by no means a build expert. However I have used the Pitmaker Vault several times. This is a vertical smoker with a water pan right over the fire box. I know you are doing a center fire box RF. one of the issues we have with the early generation Vaults is flash grease fires. If the water pan gets dry and you open the door to check the meat. Well it gets real exciting!!! So my concern is pooling all the grease with no water over the fire box and then opening the door and then you have some excitement on your hands.

Just a thought. What if you did your heat deflector between the RF plate and fire box as you talked. But you make your high point centered over the fire box so the grease drains away from the hottest point. Yes that would make 2 drains for the grease. More work, but safer from flash fires.
post #48 of 72
I kinda like the idea of the RF plate tapering down to the center front with the drain in the center front ... the heat then flows easier and even to both sides as the RF plate angles upwards from center towards the ends...
post #49 of 72
Thread Starter 

This is what is great about this site. Everybody coming up with real  viable alternatives. Thanks you guys.


If I understand you Bubonehead, you're talking about tapering the heat shield only and there I think you're right on to what I'm trying to do, Right?


Jarjarchef with the grease traps are you talking about the RF plate? I have dampers between the firebox and smoke chamber that are actuated from one end of the smoker. The control rod runs along the bottom to the outside of the smoke chamber, so that would get in the way of a drain. Of course the second drain could be offset.


JckDanls 07 I like the idea of one drain, ease of use, one bucket, etc. and a center drain would be more symmetrical which is what a center fire RF is, I like symmetry, but the firebox is in the way for a centered drain. I believe the RF plate will line up almost even to the top of firebox. I think this means the RF plate will do more work than on a traditional RF smoker. Making control more critical.


Ok I finally read everything through a couple of times and I see your all on a general thread here. And it make sense that heat runs uphill. And Dave is always talking about frictional loss in the air flow. So it's a bit more work, but as I'm trying to make a center fired RF any design that give more control is well worth it.



post #50 of 72

DB, evening.....   A center feed FB is unique to a smoker...  Since the heat/smoke/air flow is split into 2 directions, the RF plate can be lowered to less than 3/4 the area under it in the calculator...   surface area is reduced by more than half and the distance traveled is less than half....   A lot less friction to account for....   More space for food racks etc...   Hope that makes sense.... 



post #51 of 72
Thread Starter 

Thanks Dave. I hadn't taken that into account. I am going to cut the 1/4" angle loose and lower it to just above the heat shield. That will give me a little more room for the grill area. By your calculations would this also mean that I should make the spaces at either end of the RF plate smaller? On Dragon's Breath they are probably a little large for a center fire. Will it make much difference with more or less flow at each end? Anything I can do to get the control has to be good. And I'm trying to get the best of all designs combined into one. I made the firebox so large on this build I hope to get at least 10 hours of smoking with one fire up.



post #52 of 72

Honestly I was talking about the RF plate itself. I believe that by doing it this way and lowering it as Dave said, you will not need the additional heat shield. Build a dam across the front so that you create a volume that can be filled with water as an option. Take a quick look back at my build and picture the RF plate rotated 90 degrees counter clockwise.



post #53 of 72
Thread Starter 

Hey sometimes a misconception yields valuable information. I looked back over your build Bubbonehead and you made your unit seriously heavy duty! with the 1/2" RF plate, gives a massive heat sink, and I like the controls you incorporated into your smoker. I was thinking about putting a damper at each end of the RF plate similar to what you did between your firebox and smoke chamber. More work but it definitely would give more control. But I don't have any 1/2" plate and it would add to the overall weight. On this build there will also be a full size Santa Maria style grill. It will have to be toed and I am trying to keep within the weight range of a 1/2 ton pickup.



post #54 of 72
Yes I was referring to the RF plate and the grease on it. Just a theory my FIL and I have been playing with on the center firebox RF smoker. We were kicking around the idea of an adjustable plate to go between the firebox opening and the RF plate. We were thinking about extending the the adjustable plate about 30% of the fire box width to either side. This way the grease would drain to either side and lower the chance of flash fires and we would use the radiant heat from the adjustable plate to heat the center of the RF plate. Due to the friction we were also planning on keeping the area under the RF plate the same and the openings at either end at 75% of recommended so we could add dampers at either end to allow us to control the air flow and maybe control temps too.......again all theorys we were kicking around with some 12oz encouragement biggrin.gif

I am looking forward to seeing where things go and what you find out....
post #55 of 72
I think your hinges might be a problem built with stainless and carbon. I don't know the exact numbers in my head, but they expand at different rates with heat. This might cause them to jam when you fire it up.
post #56 of 72
Thread Starter 

Rasimmo you're right about the differences in thermal expansion, but I drilled the pipes .016" over size so there would be room for a good fit. All that is needed is a 1/64" over sized drill bit.    I have made 3 different size hinges and found the bits very reasonable on eBay. That being said I still do not believe that the thermal expansion differences have a critical effect on the hinges. If you were to use a stainless hinge then wouldn't that have more effect than one that was half stainless? The real reason I went 1/64" over on the hole was I use between 4 and 6 pipes on each hinge and drill them out on my drill press. With only .016" clearance a small misalignment on the drill vice will eat up most of that. 

I have been using Dragon's Breath for almost 2 years now and no problems seizing up.

Back a while I was fitting up about 80 feet of 4" stainless tubing and had it all tacked except for the last fit at the end of the day. This was in Merced Ca. and it was probably over 100 degrees. The next morning it was overcast and cooled down to around 60 degrees. The tubing was now about 1/4" short of the fit. This is .0625" wall tube and you have to have a good fit. We waited 4 days for the sun to come out and it never did. So I took the pump apart and used a rose bud to blow hot air into the tubing and she crept right up and fit as tight as could be. I'm not sure how far mild steel would have traveled under those circumstances, but you know it would have been less.



post #57 of 72
Thread Starter 

Got the RF plate welded in with dam and water test. Ready to stick it!



It's better to have too much trailer. I found out the hard way.


The smoke chamber over the trailer for measurements.


I had to remove 34" off the back of the trailer and I will remove 38" from the front. Then it will be just right.

There are brakes at all 4 wheels. This one will hold everything a smoker needs.



post #58 of 72

Love the pictures keep them coming !!!!




post #59 of 72

so with the center mounted firebox,will the stack be mounted directly center?im not sure how the heat will be the same temp,from each end?









life is like a box of chocolates,you never know what your gonna get next!

post #60 of 72
Thread Starter 

Yeah ribrustler67. mounted dead center. If my calcs are right..... it should be close on both ends and the center. My first center fired had the RF plate lower on the left side. The left side had the coolest temps. This time the Rf plate is level and with the heat shield under center of the Rf plate I'm thinking the temps will be closer through out.


Here's the trailer cut down and boxed in, ready for the smoker!


gary s I now you like pictures so do I.

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